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Manufacturing process of textile industries (Printing and dyeing process of fabrics)

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Muhammad Umair Akram
Muhammad Umair Akram

This document is actually based practical research That was completed during my internship in AMSONS textiles mills (pvt.) ltd Karachi, Sindhi, Pakistan. This document will really help you in your studies and will make it easy for you to understand about the process that are usually followed during printing and dyeing of fabric. In this document the quality control procedures of textile industry are also discussed.

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Manufacturing Process of Textiles Mills Muhammad Umair Akram#1 1# Industrial & Manufacturing Engineering Department, NED University of Engineering and Technology University Road, Karachi-75270., Sindh, Pakistan 1im079um@gmail.com 2umair.an@ymail.com The flow chart of manufacturing process of AMSONS Textile Mill (Printing & Dying of Gary Fabric) that I observe during my internship is as follow After all these processes have done the finished fabric is sent to the market. Grey Fabric Inspection Singeing & Desizing Bleaching Mercerizing (If required) Setting (On Stenter) Inspection Dyeing OR Printing Washing (On PAD steam if dyed) Inspection Curing (If printed) Finish (On Stenter) Calendar Sanforising (If required)
I. INSPECTION OF GREY FABRIC The manufacturing of anything requires raw material AMSONS textile mill (Dying & Printing of Fabric) uses the grey fabric as the raw material. This is usually collected by the waving department or sometimes by the party. The first step of manufacturing process is to inspect the raw material that is as per required? Grey fabric is inspected as 1. Thread Counting i.e. (warp & weft) In the fabric manufacturing process thread selection is important to get the proper GSM of fabric it counted by Pick glass. 2. Weight/sq. meter yarn 3. Yarn count In this process we take the 10 threads of warp and ten threads of weft and then they are weighted separately. And then put in to this formula Yarn count = number of threads*length of threads (cm)*0.0059/weight of threads in (gm.) Here the inspection of the grey fabric is completed. II. SINGEING & DESIZING The process of singeing is carried out for the purpose of removing the loose hairy fibres protruding from the surface of the cloth, thereby giving it a smooth, even and clean looking face. Singeing is an essential process for the goods or textile material which will be subjected to mercerizing, dyeing and printing to obtain best results from these processes. The fabric passes over brushes to raise the fibres, and then passes over a plate heated by gas flames. When done to fabrics containing cotton, this results in increased wettability, better dyeing characteristics, improved reflection, no "frosty" appearance, a smoother surface, better clarity in printing, improved visibility of the fabric structure, less pilling and decreased contamination through removal of fluff and lint. Gas singeing is used in AMSONS textile industry. In gas singeing, a flame comes into direct contact to the fabric and burn the protruding fibre. Here, flame height and fabric speed is the main concern to minimize the fabric damage. Singeing is a mechanical process by which hairy, loose fibres are removed from the surface of the textile material either by heating or burning to make the material smoother and lustrous. Desizing is the process of removal of sizing material. Different types of sizing materials are being used in industries. The sizing material is of no use after the yarn is being woven into fabric. Desizing is the process of removing sizing materials from the fabric, which is applied in order to increase the strength of the yarn which can withstand with the friction of loom. Fabric which has not been desized is very stiff and causes difficulty in its treatment with different solution in subsequent processes. After singeing operation the sizing material is removed by making it water soluble and washing it with warm water. Desizing is done by the oxidative method (chlorine, chloride, bromite, hydrogen peroxide) It is generally assumed that it is necessary to remove the sizing material to achieve the satisfactory levelness of bleaching, dyeing & printing process. Improper desizing process may cause the faulty dyeing of fabric like un-even dyeing and variation in shades and irregular printing. After these steps, fabric is kept on rotation for 8 to 12 hours continuously. The degree of proper desizing is determined by extremely sensitive iodine test and the degree of sizing is called Tigawa. III. BLEACHING Bleaching improves whiteness by removing natural coloration and remaining trace impurities from the cotton; the degree of bleaching necessary is determined by the required whiteness and absorbency. Cotton being a vegetable fibre will be bleached using an oxidizing agent, such as dilute sodium hypochlorite or dilute hydrogen peroxide or caustic soda. If the fabric is to be dyed a deep shade, then lower levels of bleaching are acceptable. However, for white bed sheets and medical applications, the highest levels of whiteness and absorbency are essential. After scouring and bleaching, optical brightening agents (OBA) are applied to make the textile material appear whiter. The bleaching process that is followed in AMSONS textile is initially the desized fabric is washed/passed through the tanks of bleaching agent whose recipe is (12gm/l caustic soda + 5gm/l weighting agent + 7gm/l stabilizer + 1gm/l sick ester) then this fabric is steam heated at about 95⁰C for 30 to 40 mints then after fabric is passed through the water tanks and washed. Thus the fabric is bleached. IV. INSPECTION OF BLEACHED FABRIC When the fabric is completely bleached its sample is than send to the printing & dyeing lab where its inspection takes place. The following three tests are done on the bleached fabric. 1. Absorbency 2. Tigawa 3. PH Absorbency test is carried out after bleaching. A scale is stamped on the sample and dropped in to the liquid for 1 mint the fabric absorbs the liquid. For the better quality level the absorbency level must be higher or equal to 3. Since the hydrogen per oxide is harm full to the human body it is therefore, necessary to test the Tigawa according to the scale defined the less the number of Tigawa the better the quality it gains. This test is done by dropping iodine liquid on the fabric, and then matches the colour with pre-defined scale. For better quality level Tigawa must be less than 4. PH test is necessary to control the PH of the dyeing bath because it affects the exhaustion and fiction rate some dyeing process are carried out in the alkaline medium and some are done in acidic medium. It depends on the dye characteristic and what type of dyes is used for which fibre. In general the PH level must be greater than 6. V. MERCERIZING Mercerization is a treatment for cotton fabric and thread that gives fabric or yarns a lustrous appearance and strengthens them. The process is applied to cellulosic materials like cotton or hemp. A further possibility is mercerizing during which the fabric is treated with sodium hydroxide solution to cause swelling of the fibres. This results in improved lustre, strength and dye affinity. Cotton is mercerized under tension, and all alkali must be washed out before the tension is released or shrinkage will take place. Mercerizing can take place directly on grey cloth, or after bleaching. (This is an optional step, performed when party requires) Note: During our whole internship mercerizing process was not performed. VI. SETTING
The setting of fabric is done on the Stenter machine. Stenter is used for open form fabric. After passing the open compactor fabric enters into the Stenter. Cotton fabric shrinks width wise and weft distorted due to bleaching and dyeing process. The main purpose of the fabric is to starch the fabric width wise and recover the uniform width. The main purpose of setting is to set the width of the fabric so that we are able to print or dye the fabric according to requirement. The function of Stenter is 1. Width of fabric is controlled by the Stenter. 2. Finishing chemicals are applied on fabric by Stenter. 3. Shrinkage property is controlled by the Stenter. 4. GSM of fabric is controlled by the Stenter. 5. Fabric is dried by the stentring process. VII. DYEING & PRINTING Dyeing is the process of adding colour to textile products like fibres, yarns, and fabrics. Dyeing is normally done in a special solution containing dyes and particular chemical material. After dyeing, dye molecules have uncut chemical bond with fibre molecules. The temperature and time controlling are two key factors in dyeing. Dyes are used for colouring the fabrics. Dyes are molecules which absorb and reflect light at specific wavelengths to give human eyes the sense of colour. There are two major types of dyes - natural and synthetic dyes. The natural dyes are extracted from natural substances such as plants, animals, or minerals. Synthetic dyes are made in a laboratory. Chemicals are synthesized for making synthetic dyes. Some of the synthetic dyes contain metals too. Fabric dyeing, also known as piece dyeing, is dyeing fabric after it has been constructed. It is economical and the most common method of dyeing solid coloured fabrics. The decision regarding colour can be made after the fabric has been manufactured. Thus, it is suitable for quick response orders. Dye penetration may not be good in thicker fabrics, so yarn dyeing is sometimes used to dye thick fabrics in solid colours. Various types of dyeing machines are used for piece dyeing. The selection of the equipment is based on factors such as dye and fabric characteristics, cost, and the intended end use. In AMSONS textile industry the dyes are made or tested in the lab and then passed for the manufacturing process and the machine used is Thermo-sol dyeing machine. The process followed is continuous dyeing process in piece dyeing, which is used primarily for fabrics that are to be a solid colour; a continuous length of dry cloth is passed full- width through a trough of hot dye solution. The cloth then goes between padded rollers that squeeze in the colour evenly and removes the excess liquid. In one variation of this basic method, the fabric, in a rope-like coil, is processed on a reel that passes in and out of a dye beck or vat. Textile printing is referred as localized dyeing. It is the application of colour in the form of a paste or ink to the surface of a fabric, in a predetermined pattern. Printing designs onto already dyed fabric is also possible. In properly printed fabrics the colour is bonded with the fibre, so as to resist washing and friction. Textile printing is related to dyeing but, whereas in dyeing proper the whole fabric is uniformly covered with one colour, in printing one or more colours are applied to it in certain parts only, and in sharply defined patterns. In printing, wooden blocks, stencils, engraved plates, rollers, or silkscreens can be used to place colours on the fabric. Colorants used in printing contain dyes thickened to prevent the colour from spreading by capillary attraction beyond the limits of the pattern or design. Printing process used in AMSONS Textile industries uses the digital printing mechanism. Digital textile printing is described as any ink jet based method of printing colorants onto fabric. Most notably, digital textile printing is referred to when identifying either printing smaller designs or printing larger designs onto large format rolls of textile. In AMSONS Textile Industry Usually “Zimmer” machine is used for printing of fabric which is based on jet ink technique. On the machine equal to the equal to the number of colours used in the design engraved rollers are placed on the machine so that all colours are printed separately on the fabric thus at the end a single design as obtained. VIII. WASHING & CURING Second step after dyeing is of drying of fabric which is done on “PAD Steam” machine and then the fabrics goes to the chemical pad at the third step and finely the dyestuff is fixed on the fabric. Washing of Dyed fabric is done on the PAD Steam. This process is performed with sulphur dye. Fabric picks the chemical and goes to the steamer for fixation. At the end the fabric goes through the washing pads to remove the un-fixed dyestuff. If the fabric is printed so it is needed to be cured. Curing is the process of hardening the colour on to the fabric so that it won’t remove after washing. The temperature must get hot enough to firstly evaporate the water based medium, then set the pigments - about 150°C [depending on the material to be heat set], Hair driers & household tumble driers are not suitable as they do not get hot enough to set the pigments. IX.INSPECTION OF PRINTED FABRIC After the printing/dyeing and curing the fabric’s sample is send to the printing and dyeing laboratory for pilling and staining i.e.(colour bleeding) tests are performed. Pilling is a fabric surface characterized by little pills of entangled fiber clinging to the cloth surface and giving the garment unsightly appearance. The pills are formed during wear and washing by the entanglement of loose fibers which protrude from the fabric surface. Under the influence of the rubbing action these
loose fibers develop into small spherical bundles anchored to the fabric by a few unbroken fibres. The samples are given a multi directional movement and rubbed against a standard fabric. After certain number of rubs, the samples are examined and the number of pills counted. This may be repeated say in stages of 500 cycles up to 3000 or 5000 and the rate of development of pills noted. Colour bleeding test is performed on the dry and wet cotton called “Percale cotton”. A piece of percale cotton is rubbed on the printed fabric normally for 10 cycles and the degree of colour bleeding is counted against predefined scale. This number must be less than 3. X. FINISHING Textile finishing is the term used for a series of processes to which all bleached, dyed, printed and certain grey fabrics are subjected before they put on the market. The object of textile finishing is to render textile goods fit for their purpose or end- use and/or improve serviceability of the fabric. Finishing on fabric is carried out for both aesthetic and functional purposes to improve the quality and look of a fabric. Fabric may receive considerable added value by applying one or more finishing processes. The machines used for finishing process in AMSONS Textile Industry are Stenter and calendar. The purpose of the Stenter machine is to bringing the length and width to pre determine dimensions and also for heat setting and it is used for applying finishing chemicals and also shade variation is adjusted. The main function of the Stenter is to stretch the fabric widthwise and to recover the uniform width. The fabric is collected from the batcher to the scary and then it is passed through the pads where the finishes are applied and sometimes shade variation is corrected. The fabric is entered into the mahlo (weft straightener) the function of the mahlo is to set the bow and also weave of the fabric is gripped by the clips and pins are also provided but the pins has a disadvantage that they pins make holes at the selvedge but the stretching of the pins are greater than the clips. These clips and pins are joined to endless chain. There are 8 to 10 chambers provided on the machine each chamber contains a burner and filters are provided to separate dust from air. The circulating fans blow air from the base to the upper side and exhaust fans sucks all the hot air within the chambers. Attraction rollers are provided to stretch the warp yarn. XI. CALENDER Calendering is an operation carried out on a fabric to improve its aesthetics. The fabric passes through a series of calender rollers by wrapping; the face in contact with a roller alternates from one roller to the next. An ordinary calender consists of a series of hard and soft (resilient) bowls (rollers) placed in a definite order. The soft roller may be compressed with either cotton or wool-paper, linen paper or flax paper. The hard metal bowl is either of chilled iron or cast iron or steel. The calender may consist of 3, 5, 6, 7 and 10 rollers. The sequence of the rollers is that no two hard rollers are in contact with each other. Pressure may be applied by compound levers and weights, or hydraulic pressure may be used as an alternative. The pressure and heat applied in Calendering depend on the type of the finish required. The purposes of Calendering are to upgrade the fabric hand and to impart a smooth, silky touch to the fabric, to compress the fabric and reduce its thickness, to improve the opacity of the fabric, to reduce the air permeability of the fabric by changing its porosity, to impart different degree of luster of the fabric, and to reduce the yarn slippage. XII. SANFORISING “Sanforising allows preventing the cotton from shrinking when washed. It is carried out by compressing the cotton to reduce its shrinking capacity”. Sanforising is the process of treatment used for cotton fabrics mainly. It is a method of stretching, shrinking and fixing the woven cloth in both length and width before cutting and producing, to reduce the shrinkage which would otherwise occur after washing. The cloth is continually fed into the sanforising machine and therein moistened with either water or steam. A rotating cylinder presses a rubber sleeve against another, heated, rotating cylinder. Thereby the sleeve briefly gets compressed and laterally expanded, afterwards relaxing to its normal thickness. The cloth to be treated is transported between rubber sleeve and heated cylinder and is forced to follow this brief compression and lateral expansion, and relaxation. It is thus shrunk. The greater the pressure applied to the rubber sleeve, the less the shrinking afterwards. The process may be repeated. The aim of the process is a cloth which does not shrink significantly during clothes production by cutting, ironing, sewing or, especially, by wearing and washing the finished clothes. Cloth and articles made from it may be labeled to have a specific shrink-proof value. Note: During our whole internship sanforising process was not performed. Then at the end this finished fabric is sent to the market for seal.

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Manufacturing process of textile industries (Printing and dyeing process of fabrics)

  • 1. Manufacturing Process of Textiles Mills Muhammad Umair Akram#1 1# Industrial & Manufacturing Engineering Department, NED University of Engineering and Technology University Road, Karachi-75270., Sindh, Pakistan 1im079um@gmail.com 2umair.an@ymail.com The flow chart of manufacturing process of AMSONS Textile Mill (Printing & Dying of Gary Fabric) that I observe during my internship is as follow After all these processes have done the finished fabric is sent to the market. Grey Fabric Inspection Singeing & Desizing Bleaching Mercerizing (If required) Setting (On Stenter) Inspection Dyeing OR Printing Washing (On PAD steam if dyed) Inspection Curing (If printed) Finish (On Stenter) Calendar Sanforising (If required)
  • 2. I. INSPECTION OF GREY FABRIC The manufacturing of anything requires raw material AMSONS textile mill (Dying & Printing of Fabric) uses the grey fabric as the raw material. This is usually collected by the waving department or sometimes by the party. The first step of manufacturing process is to inspect the raw material that is as per required? Grey fabric is inspected as 1. Thread Counting i.e. (warp & weft) In the fabric manufacturing process thread selection is important to get the proper GSM of fabric it counted by Pick glass. 2. Weight/sq. meter yarn 3. Yarn count In this process we take the 10 threads of warp and ten threads of weft and then they are weighted separately. And then put in to this formula Yarn count = number of threads*length of threads (cm)*0.0059/weight of threads in (gm.) Here the inspection of the grey fabric is completed. II. SINGEING & DESIZING The process of singeing is carried out for the purpose of removing the loose hairy fibres protruding from the surface of the cloth, thereby giving it a smooth, even and clean looking face. Singeing is an essential process for the goods or textile material which will be subjected to mercerizing, dyeing and printing to obtain best results from these processes. The fabric passes over brushes to raise the fibres, and then passes over a plate heated by gas flames. When done to fabrics containing cotton, this results in increased wettability, better dyeing characteristics, improved reflection, no "frosty" appearance, a smoother surface, better clarity in printing, improved visibility of the fabric structure, less pilling and decreased contamination through removal of fluff and lint. Gas singeing is used in AMSONS textile industry. In gas singeing, a flame comes into direct contact to the fabric and burn the protruding fibre. Here, flame height and fabric speed is the main concern to minimize the fabric damage. Singeing is a mechanical process by which hairy, loose fibres are removed from the surface of the textile material either by heating or burning to make the material smoother and lustrous. Desizing is the process of removal of sizing material. Different types of sizing materials are being used in industries. The sizing material is of no use after the yarn is being woven into fabric. Desizing is the process of removing sizing materials from the fabric, which is applied in order to increase the strength of the yarn which can withstand with the friction of loom. Fabric which has not been desized is very stiff and causes difficulty in its treatment with different solution in subsequent processes. After singeing operation the sizing material is removed by making it water soluble and washing it with warm water. Desizing is done by the oxidative method (chlorine, chloride, bromite, hydrogen peroxide) It is generally assumed that it is necessary to remove the sizing material to achieve the satisfactory levelness of bleaching, dyeing & printing process. Improper desizing process may cause the faulty dyeing of fabric like un-even dyeing and variation in shades and irregular printing. After these steps, fabric is kept on rotation for 8 to 12 hours continuously. The degree of proper desizing is determined by extremely sensitive iodine test and the degree of sizing is called Tigawa. III. BLEACHING Bleaching improves whiteness by removing natural coloration and remaining trace impurities from the cotton; the degree of bleaching necessary is determined by the required whiteness and absorbency. Cotton being a vegetable fibre will be bleached using an oxidizing agent, such as dilute sodium hypochlorite or dilute hydrogen peroxide or caustic soda. If the fabric is to be dyed a deep shade, then lower levels of bleaching are acceptable. However, for white bed sheets and medical applications, the highest levels of whiteness and absorbency are essential. After scouring and bleaching, optical brightening agents (OBA) are applied to make the textile material appear whiter. The bleaching process that is followed in AMSONS textile is initially the desized fabric is washed/passed through the tanks of bleaching agent whose recipe is (12gm/l caustic soda + 5gm/l weighting agent + 7gm/l stabilizer + 1gm/l sick ester) then this fabric is steam heated at about 95⁰C for 30 to 40 mints then after fabric is passed through the water tanks and washed. Thus the fabric is bleached. IV. INSPECTION OF BLEACHED FABRIC When the fabric is completely bleached its sample is than send to the printing & dyeing lab where its inspection takes place. The following three tests are done on the bleached fabric. 1. Absorbency 2. Tigawa 3. PH Absorbency test is carried out after bleaching. A scale is stamped on the sample and dropped in to the liquid for 1 mint the fabric absorbs the liquid. For the better quality level the absorbency level must be higher or equal to 3. Since the hydrogen per oxide is harm full to the human body it is therefore, necessary to test the Tigawa according to the scale defined the less the number of Tigawa the better the quality it gains. This test is done by dropping iodine liquid on the fabric, and then matches the colour with pre-defined scale. For better quality level Tigawa must be less than 4. PH test is necessary to control the PH of the dyeing bath because it affects the exhaustion and fiction rate some dyeing process are carried out in the alkaline medium and some are done in acidic medium. It depends on the dye characteristic and what type of dyes is used for which fibre. In general the PH level must be greater than 6. V. MERCERIZING Mercerization is a treatment for cotton fabric and thread that gives fabric or yarns a lustrous appearance and strengthens them. The process is applied to cellulosic materials like cotton or hemp. A further possibility is mercerizing during which the fabric is treated with sodium hydroxide solution to cause swelling of the fibres. This results in improved lustre, strength and dye affinity. Cotton is mercerized under tension, and all alkali must be washed out before the tension is released or shrinkage will take place. Mercerizing can take place directly on grey cloth, or after bleaching. (This is an optional step, performed when party requires) Note: During our whole internship mercerizing process was not performed. VI. SETTING
  • 3. The setting of fabric is done on the Stenter machine. Stenter is used for open form fabric. After passing the open compactor fabric enters into the Stenter. Cotton fabric shrinks width wise and weft distorted due to bleaching and dyeing process. The main purpose of the fabric is to starch the fabric width wise and recover the uniform width. The main purpose of setting is to set the width of the fabric so that we are able to print or dye the fabric according to requirement. The function of Stenter is 1. Width of fabric is controlled by the Stenter. 2. Finishing chemicals are applied on fabric by Stenter. 3. Shrinkage property is controlled by the Stenter. 4. GSM of fabric is controlled by the Stenter. 5. Fabric is dried by the stentring process. VII. DYEING & PRINTING Dyeing is the process of adding colour to textile products like fibres, yarns, and fabrics. Dyeing is normally done in a special solution containing dyes and particular chemical material. After dyeing, dye molecules have uncut chemical bond with fibre molecules. The temperature and time controlling are two key factors in dyeing. Dyes are used for colouring the fabrics. Dyes are molecules which absorb and reflect light at specific wavelengths to give human eyes the sense of colour. There are two major types of dyes - natural and synthetic dyes. The natural dyes are extracted from natural substances such as plants, animals, or minerals. Synthetic dyes are made in a laboratory. Chemicals are synthesized for making synthetic dyes. Some of the synthetic dyes contain metals too. Fabric dyeing, also known as piece dyeing, is dyeing fabric after it has been constructed. It is economical and the most common method of dyeing solid coloured fabrics. The decision regarding colour can be made after the fabric has been manufactured. Thus, it is suitable for quick response orders. Dye penetration may not be good in thicker fabrics, so yarn dyeing is sometimes used to dye thick fabrics in solid colours. Various types of dyeing machines are used for piece dyeing. The selection of the equipment is based on factors such as dye and fabric characteristics, cost, and the intended end use. In AMSONS textile industry the dyes are made or tested in the lab and then passed for the manufacturing process and the machine used is Thermo-sol dyeing machine. The process followed is continuous dyeing process in piece dyeing, which is used primarily for fabrics that are to be a solid colour; a continuous length of dry cloth is passed full- width through a trough of hot dye solution. The cloth then goes between padded rollers that squeeze in the colour evenly and removes the excess liquid. In one variation of this basic method, the fabric, in a rope-like coil, is processed on a reel that passes in and out of a dye beck or vat. Textile printing is referred as localized dyeing. It is the application of colour in the form of a paste or ink to the surface of a fabric, in a predetermined pattern. Printing designs onto already dyed fabric is also possible. In properly printed fabrics the colour is bonded with the fibre, so as to resist washing and friction. Textile printing is related to dyeing but, whereas in dyeing proper the whole fabric is uniformly covered with one colour, in printing one or more colours are applied to it in certain parts only, and in sharply defined patterns. In printing, wooden blocks, stencils, engraved plates, rollers, or silkscreens can be used to place colours on the fabric. Colorants used in printing contain dyes thickened to prevent the colour from spreading by capillary attraction beyond the limits of the pattern or design. Printing process used in AMSONS Textile industries uses the digital printing mechanism. Digital textile printing is described as any ink jet based method of printing colorants onto fabric. Most notably, digital textile printing is referred to when identifying either printing smaller designs or printing larger designs onto large format rolls of textile. In AMSONS Textile Industry Usually “Zimmer” machine is used for printing of fabric which is based on jet ink technique. On the machine equal to the equal to the number of colours used in the design engraved rollers are placed on the machine so that all colours are printed separately on the fabric thus at the end a single design as obtained. VIII. WASHING & CURING Second step after dyeing is of drying of fabric which is done on “PAD Steam” machine and then the fabrics goes to the chemical pad at the third step and finely the dyestuff is fixed on the fabric. Washing of Dyed fabric is done on the PAD Steam. This process is performed with sulphur dye. Fabric picks the chemical and goes to the steamer for fixation. At the end the fabric goes through the washing pads to remove the un-fixed dyestuff. If the fabric is printed so it is needed to be cured. Curing is the process of hardening the colour on to the fabric so that it won’t remove after washing. The temperature must get hot enough to firstly evaporate the water based medium, then set the pigments - about 150°C [depending on the material to be heat set], Hair driers & household tumble driers are not suitable as they do not get hot enough to set the pigments. IX.INSPECTION OF PRINTED FABRIC After the printing/dyeing and curing the fabric’s sample is send to the printing and dyeing laboratory for pilling and staining i.e.(colour bleeding) tests are performed. Pilling is a fabric surface characterized by little pills of entangled fiber clinging to the cloth surface and giving the garment unsightly appearance. The pills are formed during wear and washing by the entanglement of loose fibers which protrude from the fabric surface. Under the influence of the rubbing action these
  • 4. loose fibers develop into small spherical bundles anchored to the fabric by a few unbroken fibres. The samples are given a multi directional movement and rubbed against a standard fabric. After certain number of rubs, the samples are examined and the number of pills counted. This may be repeated say in stages of 500 cycles up to 3000 or 5000 and the rate of development of pills noted. Colour bleeding test is performed on the dry and wet cotton called “Percale cotton”. A piece of percale cotton is rubbed on the printed fabric normally for 10 cycles and the degree of colour bleeding is counted against predefined scale. This number must be less than 3. X. FINISHING Textile finishing is the term used for a series of processes to which all bleached, dyed, printed and certain grey fabrics are subjected before they put on the market. The object of textile finishing is to render textile goods fit for their purpose or end- use and/or improve serviceability of the fabric. Finishing on fabric is carried out for both aesthetic and functional purposes to improve the quality and look of a fabric. Fabric may receive considerable added value by applying one or more finishing processes. The machines used for finishing process in AMSONS Textile Industry are Stenter and calendar. The purpose of the Stenter machine is to bringing the length and width to pre determine dimensions and also for heat setting and it is used for applying finishing chemicals and also shade variation is adjusted. The main function of the Stenter is to stretch the fabric widthwise and to recover the uniform width. The fabric is collected from the batcher to the scary and then it is passed through the pads where the finishes are applied and sometimes shade variation is corrected. The fabric is entered into the mahlo (weft straightener) the function of the mahlo is to set the bow and also weave of the fabric is gripped by the clips and pins are also provided but the pins has a disadvantage that they pins make holes at the selvedge but the stretching of the pins are greater than the clips. These clips and pins are joined to endless chain. There are 8 to 10 chambers provided on the machine each chamber contains a burner and filters are provided to separate dust from air. The circulating fans blow air from the base to the upper side and exhaust fans sucks all the hot air within the chambers. Attraction rollers are provided to stretch the warp yarn. XI. CALENDER Calendering is an operation carried out on a fabric to improve its aesthetics. The fabric passes through a series of calender rollers by wrapping; the face in contact with a roller alternates from one roller to the next. An ordinary calender consists of a series of hard and soft (resilient) bowls (rollers) placed in a definite order. The soft roller may be compressed with either cotton or wool-paper, linen paper or flax paper. The hard metal bowl is either of chilled iron or cast iron or steel. The calender may consist of 3, 5, 6, 7 and 10 rollers. The sequence of the rollers is that no two hard rollers are in contact with each other. Pressure may be applied by compound levers and weights, or hydraulic pressure may be used as an alternative. The pressure and heat applied in Calendering depend on the type of the finish required. The purposes of Calendering are to upgrade the fabric hand and to impart a smooth, silky touch to the fabric, to compress the fabric and reduce its thickness, to improve the opacity of the fabric, to reduce the air permeability of the fabric by changing its porosity, to impart different degree of luster of the fabric, and to reduce the yarn slippage. XII. SANFORISING “Sanforising allows preventing the cotton from shrinking when washed. It is carried out by compressing the cotton to reduce its shrinking capacity”. Sanforising is the process of treatment used for cotton fabrics mainly. It is a method of stretching, shrinking and fixing the woven cloth in both length and width before cutting and producing, to reduce the shrinkage which would otherwise occur after washing. The cloth is continually fed into the sanforising machine and therein moistened with either water or steam. A rotating cylinder presses a rubber sleeve against another, heated, rotating cylinder. Thereby the sleeve briefly gets compressed and laterally expanded, afterwards relaxing to its normal thickness. The cloth to be treated is transported between rubber sleeve and heated cylinder and is forced to follow this brief compression and lateral expansion, and relaxation. It is thus shrunk. The greater the pressure applied to the rubber sleeve, the less the shrinking afterwards. The process may be repeated. The aim of the process is a cloth which does not shrink significantly during clothes production by cutting, ironing, sewing or, especially, by wearing and washing the finished clothes. Cloth and articles made from it may be labeled to have a specific shrink-proof value. Note: During our whole internship sanforising process was not performed. Then at the end this finished fabric is sent to the market for seal.